1. Field of the Invention
The present invention relates to a cutting tool, particularly to a reamer.
2. Background Art
A reamer is a machining tool, particularly a cutting tool for enlarging or contouring a pre-existing hole in a workpiece by rotational and axial cutting. Reamers are utilized for removing a minimal amount of material from a workpiece, in comparison to a drill bit. When a particular application requires a hole that is machined to a tight tolerance, a drill bit, a gundrill or the like is utilized for defining the pre-existing hole by performing the majority of material removal, and a reamer is utilized for enlarging the pre-existing hole within the desired machining tolerance. Of course reamers may be utilized for enlarging a pre-existing hole that was generated by manufacturing processes other than a cutting operation, such as a hole developed in the fabrication of the workpiece.
Commonly bored holes that require a reamer for finishing the machining operation include, but are not limited to, valve guide bores, axle case bores, lifter bores, transmission carriers, and many other high precision applications.
Manufacturing processes commonly favor tools or tooling that may perform the desired job within the quickest time feasible with a high quality performance, thereby satisfying throughput and quality specifications. Accordingly, cutting tools such as reamers are often used in high speed operations experiencing high cutting pressures and relatively large amounts of heat, thereby limiting the life of a particular tool. Conventional reamers are characterized by a relatively high cost to produce and therefore are commonly remachined or reground to be reused after a sufficient amount of wear has been imparted on the tool. Due to the machining tolerances demanded upon reamers and the throughputs required of the machined workpieces, prior art reamers present a generally high cost in manufacturing environments due to the costs incurred in obtaining reamers, regrinding reamers and replacing reamers.
The prior art has recognized a need to fluctuate the loads imparted upon flutes formed within the reamer, and commonly such fluctuation is provided by “breaking up the flutes” by spacing cutting edges of the reamer unevenly about the reamer. The spacing is slight and is achieved by offsetting each flute in a reamer by two degrees or less to avoid equal spacing of the cutting edges.
Prior art reamers are generally characterized in two categories, straight flute reamers and helical flute reamers. Prior art reamers generally comprise an array of flutes formed therein, each providing a cutting edge at a distal end of a reamer body. Straight flute reamers include an array of straight flutes formed longitudinally therein and helical flute reamers include an array of helical flutes formed therein in a left hand direction for utilization of the reamer in a right hand rotational cutting direction. Some machining applications require that a particular hole being machined by both a straight flute reamer and a helical flute reamer to provide a hole within a desired tolerance. Accordingly, the prior art has also provided reamers having arrays of both straight flutes and helical flutes with cutting edges stepped axially relative to one another, such that a workpiece may experience a first cutting operation and subsequently a second cutting operation provided by a common reamer.
A goal of the present invention is to provide a reamer that machines within tolerances demanded in manufacturing environments and maximizes the life of the reamer by minimizing machining loads and heat experienced by the reamer and the associated work piece.